1. Field of the Invention
This invention relates to an improvement in a matrix-type liquid-crystal display panel in which thin-film transistors are used as address display elements, and more particularly to an improvement in the pattern of wiring to connect the electrodes of thin-film transistors.
2. Description of the Prior Art
One example of a matrix-type liquid-crystal display panel of the conventional type in which reverse stagger-type thin-film transistors are used as the address display elements is shown in FIGS. 3 and 4. FIGS. 4a and 4b are cross-sectional views taken at lines O-P and Q-R of FIG. 3, respectively.
In such a liquid-crystal display panel, a substrate-protective film 2 is formed on an insulating substrate 1. On top of the substrate-protective film 2, there are provided, in this order, a gate electrode 3, a gate insulating film 4, an amorphous silicon film (a-Si film) 5, a protective insulating film 6, an n.sup.+ a-Si film 7, and a source electrode and drain electrode 8, by which a reverse stagger-type thin-film transistor is formed. The picture-element electrodes 9 for display are electrically connected to the source or drain electrodes 8. In FIG. 4a, reference numeral 10 shows a protective film.
In this kind of a matrix-type liquid-crystal display panel, vertical scanning signals are supplied to a plurality of signal wires, each of which is connected to the wiring pattern 3a in the transverse direction of FIG. 3, the said wiring pattern being further connected to the gate electrode 3 of each thin-film transistor. On the other hand, picture signals are supplied to a plurality of signal wires, each of which is connected to the source wiring pattern 8a through the wiring pattern 8b in the longitudinal direction of FIG. 3, the said source wiring pattern being further connected to the source electrode of each thin-film transistor. The liquid crystals are driven by the passage of electricity in order through the picture-element electrode 9 of each thin-film transistor.
In the conventional matrix-type liquid-crystal display panel, the wiring patterns 3a, 8a, and 8b that are connected to the electrodes 3 and 8 of the thin-film transistors are in some cases overetched during the etching step in the manufacturing process. In such cases, the width of the wiring patterns 3a, 8a, and 8b becomes narrower, and in a severe case, these wiring patterns cause disconnection. As a result, the resistance of the wiring becomes high, and the level of the signal goes to decay; disconnections give rise to line defects, so that the display panel cannot be used in practice. For that reason, the production yield of matrix-type liquid-crystal display panels is greatly decreased.